1. Field of the Invention
This invention relates to a structured aqueous based heavy duty liquid detergent formulation containing a suspended bleach along with selected stability enhancers.
Liquid detergent products have become a large segment of the U.S. detergent market. Their market share in the past several years has more than doubled. Currently marketed liquid detergents contain built-in softening in the wash as well as enzymes for added stain removal. No completely formulated liquid detergents however, contain a completely satisfactory bleach.
Liquid bleach adjuncts which are to be added separately to the wash, containing hypochlorite or hydrogen peroxide are established, successful products. A low pH surfactant-structured liquid containing 1,12 diperoxydodecanedioic acid (DPDA), has been patented by Humphreys et al. in U.S. Pat. No. 4,642,198. A structured aqueous system has been employed in this bleach adjunct out due to the low pH and low amount of surfactant usually employed, the adjunct product cannot be used alone to accomplish washing.
The high concentrations of surfactants which must be included in a fully formulated liquid detergent to clean during the wash generally make it difficult to prepare an appropriately structured liquid. Structuring, however, is necessary to suspend the particulate bleach and, thus, minimize settling and other types of instability. Structured liquids are well known in the art and are described more fully below. Further, the large amount of surfactant required usually increases the viscosity of structured liquids to unacceptable levels. The viscosity, thus, must be decreased to a commercially acceptable level while still retaining the suspending characteristics of the structured liquid.
An additional difficulty is that the suspended bleach particles must not be too soluble in the product or the bleach may react with included organic materials. It is, thus, desirable to further stabilize the bleach by decreasing the pH of the concentrated composition to decrease the solubility of the bleach particles. A low pH, however, is not optimal for washing and, thus, it must be capable of increasing substantially on dilution when the product is used so that normal alkaline wash pH's can prevail.
It was, thus, desireable to formulate an aqueous based heavy duty detergent which contains relatively stable bleach and high levels of surfactant, yet still retains the suspending properties of a structured liquid while incorporating acceptable viscosity characteristics.